1. Field of the Invention
The present invention relates to an ink for ink-jet recording, an ink set containing the same, and a recoding method using the same. In particular, it relates to a magenta ink for ink-jet recording having excellent storage stability of a recorded image, having high image quality of hue, color density and the like, and also having excellent discharge stability of an ink.
2. Background Art
In recent years, with spread of computers, an ink-jet printer is widely utilized in not only offices, but households in order to print and/or draw on papers, films, cloths or the like.
An ink-jet recording method includes a method of discharging liquid droplets by applying pressure from a piezo element, a method of discharging liquid droplets by generating gas bubbles in an ink by heat, a method of using an ultrasonic wave, or a method of suction discharging liquid droplets by static force. An aqueous ink, an oily ink or a solid (melting type) ink is used as those inks for ink-jet recording.
Of those inks, the aqueous ink is relatively excellent in the point of possibility of achieving good balance of production/handling property/odor/safety, and the like, as compared with the oily ink or the solid (melting type) ink. Therefore, the aqueous ink is a mainstream of the current inks for ink-jet recording.
It is required for a dyestuff used in those inks for ink-jet recording that solubility in a solvent (ink medium) is high, high density recording is possible, hue is good, fastness properties to light, heat, air, water or chemicals are excellent, fixing property to an image receiving material is good, resulting in suppressed bleeding, storage stability as an ink is excellent, there is no toxicity, purity is high, and it can be available inexpensively. However, it is extremely difficult to seek for a dyestuff satisfying the above various requirements in high level. In particular, excellent hue and fastness properties conflict with each other in many cases. It is difficult for coloring materials for magenta ink to obtain materials satisfying the above requirements. In particular, it involves difficulty to find out the dyestuff satisfying both excellent magenta hue and light fastness durable to an oxidizing atmosphere.
Therefore, despite that various dyes and pigments for ink-jet are already proposed, and are put into practical use, it is the present situation that a dyestuff satisfying the above all requirements is not yet found.
In the conventionally well known dyes or pigments, to which color index (C.I.) number is assigned, it is difficult to achieve good balance between hue and fastness properties, required in an ink for ink-jet recording.
Azo dyes derived from an aromatic amine and a five-membered heterocyclic amine, described in JP-A-55-161856 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) shown below are proposed as a dye improving fastness properties. However, those dyes have unfavorable hue in yellow and cyan regions, and therefore had the problem of deteriorating color reproducibility.
In JP-A-61-36362 and JP-A-2-212566, it is disclosed that an ink for ink-jet recording for the purpose of simultaneous pursuit of hue and light fastness properties. However, the dyestuff used in each Document is not sufficient in solubility in water where it is used as a water-soluble ink. Further, where the dyestuff described in each Document is used as a water-soluble ink for ink-jet, there is the problem in fastness properties to humidity and heat.
As a means for solving those problems, an improved magenta dyestuff and an ink using the same, described in JP-T-11-504958 (the term “JP-T” as used herein means a published Japanese translation of a PCT patent application) are proposed. However, those inks for ink-jet recording are insufficient in color reproducibility and fastness properties of output image.
Further, it was revealed that there is the case that in the case of recording an ink-jet-only glossy paper for a photographic picture quality and sticking the paper on a wall in a room, storage stability of the image quality markedly deteriorates. The present inventors presume that this phenomenon is due to any oxidizing gas in air, such as ozone. Further, the phenomenon is difficult to occur when air flow is shielded by the action of, for example, placing the paper in a glass-made frame. However, use conditions are restricted.
This phenomenon is particularly remarkable in an ink-jet-only glossy paper for photographic picture quality, and this was a great problem in the current ink-jet recording method in which photographic picture quality is one of the important characteristics.
To develop a dyestuff durable to an oxidizing gas such as ozone, the present inventors have broken away from the conventional couplers of phenol, naphthol, aniline or the like, and have reached the thought to use a nitrogen-containing heterocyclic compound as the coupler. It is found out that in the azo dyestuff comprising a pyrazole diazo component and a pyridine coupler, described in JP-A-2002-371079, WO 02/83662 A1, WO 02/83795 A1 and WO 2003/062330 A1 fastness properties are considerably improved, and it is found out that in the ink composition containing the azo dyestuff, described in Patent Document 8, ozone resistance and light resistance are considerably improved. However, those do not yet reach the sufficiently satisfactory level.
On the other hand, the above-described ink for ink-jet recording using a water-soluble dye has the above-described advantages, but is liable to bring about the disadvantage that bleeding is easy to cause in printed characters or images. In particular, bleeding markedly develops under high humidity conditions, and its resolution is demanded.